The invention relates to an oil cooler, especially for cooling the transmission oil of a motor vehicle, of the type with a channel guide for guiding the oil to be cooled through a cooling region or zone.
It has been contemplated to provide a double pipe cooler with a double pipe extending in a water tank of a motor vehicle for the cooling of the vehicle transmission oil (German DE-PS No. 1104542). In this arrangement, the region between the respective inner and outer pipes of the double pipes serve as the oil guide channel. The double pipe is subjected to flow from the cooling water led to the water tank. In this way the oil is cooled in the double pipe. The cooling capacity is decisively dependent upon the area over which the heat exchange takes place. The length of the oil travel path through the cooling region also influences the capacity of the oil cooler. These dimensions can however not be arbitrarily chosen, especially for construction of an oil cooler for motor vehicles where only limited space is available. Thus one must strive to achieve the largest possible exchange capacity using the smallest available space.
It has been proposed to increase the heat exchange capacity by providing several double pipes arranged immediately adjacent one another in a triangle with parallel extending axes, whereby the exchange capacity as compared to an oil cooler with a single double pipe is increased (German DE-OS No. 2822743). In spite of this last mentioned proposed arrangement, the resultant heat exchange capacity is insufficient for all cases. A further increase in capacity can however not be reached with the known double pipe coolers without an increase in the required construction space. Furthermore, due to the manufacturing processes it is difficult to control variations in the exchange capacity of the double pipe exchangers.
The invention is based upon the problem of developing an oil cooler, especially for the cooling of transmission oil of a motor vehicle, which avoids the above mentioned disadvantages and also makes possible a high heat exchange capacity with only small usable building space, and which increases the heat exchange capacity as compared to the prior arrangement with the utilization of a comparable building space.
The invention proposes to construct the oil guidance channel as a double walled wave-form shape folded sheet-metal housing, between which walls the oil is guided. Such a wave formed or zig-zagged formed body exhibits a significantly greater heat exchange area and therefore makes an increase in the efficiency possible as compared to the known double pipe or tube coolers, occupying the same construction volume. Further, the oil stream can be very efficiently guided through the sheet metal body. The construction is made relatively simple and also the material needed is less than for a double pipe cooler with comparable capacity.
A further advantage is obtained if the sheet metal body is constructed so as to define a restricted path for the oil. In this way the oil is led along the longest possible path through the heat exchange body so that the oil remains a relatively long time in the cooling region and is therefore efficiently cooled.
It is especially advantageous for the construction of the oil cooler if the sheet metal body is formed of two corresponding walls which are connected on their edges with each other by crimping or soldering. The connection together of the two walls can be made before or after the folding of the walls to form the wave shaped corrugations. The restricted guidance of the oil can be accomplished in an advantageous way through the pressing together and soldering of the two walls of the sheet metal body in specific positions over the length of the body or such that the so constructed seams extend alternately over a part of the width of the sheet metal walls. Through this construction the oil is guided in a zig-zag course through the sheet metal body which itself is also wave shaped or corrugated, so as to exhibit a long travel path for the oil.
It is furthermore advantageous when a turbulance inducing device is placed in the sheet metal housing. This turbulence device serves to swirl the through-flowing oil stream and thereby to increase the heat exchange coefficient. These turbulence devices have also the function to hold both walls of the folded sheet metal at a distance from one another. For this last mentioned purpose, according to other preferred embodiments, separating cams or lugs are inserted between the walls which prevent impairment of the through flow of the oil which could be otherwise caused by the formation of narrow passages in the body during disturbance of the walls during the folding process. Further embodiments of the invention include through flow openings for a cooling medium provided through the seams. These openings make it possible for the through flow of the cooling medium whereby the heat exchange of the oil cooler is promoted.
To further promote the increase in the heat exchange it is advantageous if the oil cooler is arranged at the connection pipes in a water tank of an air cooled motor vehicle radiator. It is especially preferred that the oil cooler is arranged in the region of the incoming water connection and is disposed in the stream of the cooling water flow transverse to the zig-zag folds. In this way the inflowing cooling water impinges directly onto the oil cooler so that an efficient impact stream results which promotes the heat exchange. The connection fittings can be arranged on the same sheet metal body segment of the oil cooler so that a simple construction in the water tank is possible.
According to yet other preferred embodiments the oil cooler of the invention is used not only in a water tank but rather in a cooling air stream whereby ribs can be provided between the segments of the sheet metal body to increase the heat exchange. Many of the same advantages of the higher exchange capacity with optimal utilization of the building space are also obtained with such air cooled arrangements. The sheet metal body would then be subjected to a flow of cooling air along the direction of the zig-zag folding area.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.